Field of the Invention
The present invention relates to an internal combustion engine system.
Background Art
An internal combustion engine including an in-cylinder pressure sensor is already known, as disclosed, for example, in Japanese Patent Laid-Open No. 2009-122076. In the aforementioned conventional internal combustion engine, a seal portion is provided that seals a space between an outer face of the in-cylinder pressure sensor having a cylindrical outer shape and a wall surface of a combustion chamber that surrounds the in-cylinder pressure sensor. With the aforementioned seal portion, sealing is performed by intimate contact between a tapered portion having a tapered shape that is formed on the outer face of the in-cylinder pressure sensor and a tapered portion of the wall surface of the combustion chamber that opposes the tapered portion.
A diaphragm (pressure receiving member) that receives an in-cylinder pressure is provided at one end of a cylindrical housing which the aforementioned in-cylinder pressure sensor includes. A detecting element (strain gauge element) is disposed inside the housing. A compressive load that is based on the in-cylinder pressure is input to the detecting element from the diaphragm through a pressure transmitting member, and the detecting element outputs an output in accordance with the input compressive load. The seal portion is provided at a position that is on the side of the aforementioned one end of the housing relative to the detecting element in the axial direction of the housing.
The following problem exists in a configuration such as that described in the aforementioned Japanese Patent Laid-Open No. 2009-122076 in which a seal portion is provided at a position that is further on a combustion chamber side relative to a detecting element in the axial direction of a housing. That is, with respect to a gap between the housing and the wall surface of the combustion chamber, if the sealing function of the seal portion is normal, high temperature combustion gas enters only as far as a gap that is on the tip side relative to the position at which the seal portion is provided. In contrast, if an abnormality arises in the seal portion and the sealing function declines, high temperature combustion gas will flow in as far as a gap that is further to the inner side than the seal portion. Consequently, the amount of heat received from the combustion gas by a member located along a path on which the compressive load is transmitted from the pressure receiving member to the detecting element increases. As a result, there is an increase in a detection error in the in-cylinder pressure that is attributable to thermal strain of a tip portion of the sensor that is involved in the detection of pressure from the pressure receiving member to the detecting element that is caused by a transient difference between the thermal expansion of a member (housing) on the outer side of the tip portion of the sensor and the thermal expansion of a member on the inner side thereof. Therefore, it is desirable to provide means for enabling a determination as to whether or not there is an abnormality in the sealing function of the seal portion on an actual machine.